From EP 1 229 985 B1, a liquid filter is known that has a housing containing a receiving space that can be closed with a cover for accommodating an annular filter element. The known liquid filter comprises further an inlet on the crude side, an outlet on the pure side, and a discharge line through which the receiving space can be emptied after removing the cover. In the mounted state of the liquid filter, this discharge line is arranged at the bottom at the receiving space. Further, a closure is arranged on the filter element, which closure closes the discharge line when the filter element is inserted in the receiving space and when the receiving space is closed by means of the cover. In the known liquid filter, said closure is formed by an eccentrically arranged pin axially projecting from an axial end disk of the filter element. The receiving space of the known liquid filter is closed from above with the cover, and the discharge line is formed at the bottom of the receiving space in the housing. For a simplified finding and inserting of the pin into the discharge line, a concentrically arranged and helically ascending ramp is provided, wherein the discharge line is arranged between a lower ramp end and an upper ramp end. When screwing-on the cover, through the rotation of the filter element and through the sliding of the pin along the ramp, the pin automatically finds the discharge line, can penetrate therein and close the same. In an advantageous embodiment of the known liquid filter, the ramp and the pin can interact according to the key-lock-principle so that a filter element provided with a pin adapted to the ramp can be used in such a manner that the closure finds and closes the discharge line automatically when screwing-on the cover.
With a missing filter element or when using a filter element which is not specifically adapted to the filter housing, a sufficient purification of the respective liquid for the operation of the internal combustion engine can not be ensured. Accordingly, the danger of damage to the internal combustion engine caused by contamination carried along with the respective liquid increases.